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<body>


Entity attributes management framework.

<h2>Pluggable Entity Attributes package</h2>

The package supports entity attributes management. Attributes
can be provided by plugged in providers, The implementation
caches providers results.

<h3>Clients Interface</h3>

Clients should start at {@link Turbo} class.
It allows to query for attribute values,
to determine their readiness, to write
them down and supports listening on attribute
changes.

<h3>Providers Interface</h3>

Attribute providers should start at {@link FileAttributeProvider}
implement it and register it using system filesystem at
<code>Services/FileAttributeProviders/Default</code>.

<h3>Consistency Note</h3>

It may happen that value changes at providers level, however
unnoticed by clients because the value is cached at memory
layer and framework does not check providers in such case.
<p>
It may happen only if provider does not have exclusive control
over stored data (e.g. CVS/Entries based provider and extenally
executed cvs).
<p>
Solution is that this risk is documented at attribute definition
contract and client of such contract provides to user explicit action
that synchronizes states. Contract should define <code>null</code>
value for invalidation purposes.

<h3>Attribute Definition</h3>

Both providers and clients must understand
attribute definiton they are using. The attribute
definitions are not covered by this package.

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